Networks, data centers, cloud infrastructure, etc. are realized ultimately through physical hardware. The physical hardware is used to realize networking, computing, and/or storage functions including optical/photonic networking, Time Division Multiplexing (TDM), packet switching, etc. Conventionally, there are generally two approaches for how physical hardware is deployed—through a chassis and associated modules or through a rack mounted unit. A chassis-based system includes a chassis with multiple slots and a backplane which support different modules, line cards, circuit packs, blades, etc. (for simplicity, these are referred to as modules). The chassis-based system allows deployment flexibility where modules as-needed or required are selectively inserted in the chassis. The chassis includes an electrical (Printed Circuit Board (PCB)) backplane, fixed-size modules, shared power and cooling for all of the modules, a central switch fabric such as through one or more modules, etc. Other advantages of a chassis include power installation once for the chassis, front access only, redundancy, tight coupling of software and hardware, etc.
There are several fundamental challenges, namely 1) PCB backplanes are becoming limited in their ability to support higher Serializing-Deserializer (SERDES) rates at the same Fabric-to-Module distances, 2) the industry business model that led to these types of designs is changing, 3) consumption patterns on life-cycle and depreciation practiced by network operators, that is in turn reinforced by the merchant Application Specific Integrated Circuit (ASIC) supply chain, connote requirements for greater modularity, and the like. That is, the conventional chassis-based approach is centralized with a fixed form-factor which limits flexibility in size, power, and the ability to address different applications. Further, the chassis-based approach requires a lock-in ahead of time, suboptimal faceplate use, fixed slot sizes and power, fixed cooling, fixed slot bandwidth, etc. The chassis-based approach requires a large initial investment.
The rack mounted unit is also referred to as “pizza boxes” and generally include 1-2 (or more) Rack Unit (RU or simply U and which is a standard unit of measurement of 44.5 mm or 1.75″) high completely enclosed form factor. The rack mounted unit differs from a chassis in that all of the hardware is already included as the rack mounted unit is deployed. For example, data centers realize network elements such as in a leaf/spine architecture in a completely decentralized and modular form using rack mounted units. Advantages of the rack mounted unit approach include standard interfaces, stackability, low cost, adaptability, low first-in cost and pay as you go, etc. While this provides flexibility, this approach has interconnect complexity, such as massive amounts of cabling in the front and this cabling is based on pluggable optics which lack the density achievable in chassis-based approach. Also, this approach does not include redundancy, expansion to larger systems is complex and inefficient, and each install requires a power connection.